“There are a lot races that are close to the line we're not going to win now because they're going to battle out who's going to kill grandma first, ObamaCare or Paul Ryan's budget,” said one Republican strategist who works on congressional races. “It could put the Senate out of reach. In the House it puts a bunch of races in play that would have otherwise been safe. ... It remains to be seen how much damage this causes, but my first blush is this is not good.”

Many Republicans in tough races this year, especially in the House, voted for Ryan’s proposal, which makes it hard for them to distance themselves from it.

And while Republicans are expected to keep the House, the more seats they lose, the closer the Democrats will be to a potential takeover in 2014. The Senate is too close to call; the GOP only needs to gain four seats (if President Obama wins reelection) to take control.